1. Field of the Invention
This invention relates to a recording and reproducing apparatus and more particularly to a recording and reproducing apparatus having a solid-state image sensor in which picture elements are arranged in an offset manner.
2. Description of the Related Art
The known recording and reproducing apparatuses of the kind having a solid-state image sensor include a VHS type, an 8-mm video type, an electronic still camera, etc. In the early stage of employment of the solid-state image sensor, the photosensitive part of the image sensor was formed by regularly arranging light receiving elements (or picture elements) of a square or rectangular shape in a matrix-like state. However, a demand for a higher picture quality increased. In answer to it, efforts have been made to enhance the picture quality of the solid-state image sensor. As a result, a new method of arranging the image sensor has recently been developed. According to this method, each of the picture elements is formed in a polygonal shape such as a rhombic or hexagonal shape and they are arranged with their centroids two-dimensionally offset in a so-called offset sub-Nyquist sampling structure. The picture quality can be improved by preventing the shrinkage (a decrease in sensitivity) of the light receiving area of the image sensor by this method.
However, like in the case of the image sensor which is arranged as shown in FIG. 2(a), a moire would take place if a TV signal is formed by reading the signal in a zigzag manner in the horizontal direction as indicated by full- and broken-line arrows in FIG. 2(a). To solve this problem, the TV signal must be interpolated with signals of offset picture element parts, which are, for example, points indicated by square marks if points indicated by circular marks are arranged to be sampling points. It is also necessary to provide the image sensor with a two-dimensional filter having a large signal processing part for the purpose of limiting the frequency band of the signal in the horizontal direction. Further, for the above-stated interpolation process, a frame memory is arranged to temporarily store the output of the image sensor by offset-sub-Nyquist-sampling the output.
As mentioned above, in the above-stated example of the prior art arrangement, the frame memory is arranged to temporarily store the output of the image sensor for the interpolating process. Meanwhile, an image recording and reproducing apparatus is generally provided with a frame memory which is arranged to temporarily store a reproduced signal for the purpose of processing in a given manner the reproduced signal obtained from a recording medium or for performing a special reproducing operation. It is, therefore, preferable to arrange one and the same frame memory to serve both the above-stated different purposes. However, in storing the reproduced signal, a signal obtained by sampling in an ordinary manner is stored. Therefore, in order to enable the frame memory which is arranged to temporarily store the offset-sub-Nyquist-sampled output of the image sensor to be capable of storing also the ordinary reproduced signal, the frame memory must be arranged to store the signal with the same degree of horizontal resolution as the reproduced-signal-storing frame memory. In this instance, a larger storage capacity is required for reproduction than for image sensing.
The storage capacity for reproduction can be reduced to about the same capacity required for image sensing by arranging the frame memory to store an offset-sub-Nyquist-sampled signal also in reproducing. However, such an arrangement requires a two-dimensional filtering process also for reproduction as well as for image sensing. This necessitates circuit arrangement on a larger scale.